96 



NATURE STUDY 



tnucli less readil}', the water taking up but a small amount of the 

 substance. There are other liquids such as the acids and alkalis 

 which will dissolve substances which water will not dissolve, 

 but the solvent power of water is sufficient for illustration 

 of the facts of solution, and it is water with which we have the most 

 to do. Test-tubes are the most satisfactory vessels in which to 

 make the solutions, but bottles or drinking glasses will answer 

 very well. 



After making solutions we may follow with lessons on the 

 regaining of the dissolved substances from the solutions. That 

 is done, of course, by evaporating the water which leaves the sub- 

 stance in solution behind. This is most rapidly done by heating 

 the water to boiling, when it quickly passes away. All the sub- 

 stances above suggested should be regained from their solu- 

 tions. Sugar dissolved in water exists in beets, in sugar-cane or 

 in the sap of maple trees. The juices are extracted and "boiled 



down," that is, the water is 



.^ 



Fig, 



69. Apparatus for obtaiuiug crystals 

 on strings. 



evaporated away and molasses 

 or sugar is left. 



When a substance is re- 

 gained trom solution by the 

 rapid process of boiling it is 

 left behind generally in the 

 form of a fine powder of very 

 minute crystals. If, -however, 

 we allow the evaporation to 

 go on slowly, as in an open 

 vessel in the temperature of 

 the school-room, then the 

 dissolved substance will form 

 into large, beautiful crystals. 

 If strings or slender sticks are 

 suspended in the liquid the 



